Design of Experiments

I am using Custom Design under Design of Experiments to create formulations. When JMP created the formulations for the experiment, two of the formulations were repeats with the same measurements. I was wondering if this was done on purpose or if it is something wrong that the software produced.

This can happen, but is situational. For example, suppose you only need 7 runs to estimate the model you want, but you ask JMP for 8 runs. The optimality algorithm will choose the 8th run that provides the best design, so it may be a repeat. Note that my comment assumes that you have not specifically asked for any replicates.